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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14918
Experience:  Certified on Onan and Generac generators
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Onan generator 8000 keeps surging and than after a while

Customer Question

onan generator 8000 keeps surging and than after a while shuts down
Submitted: 1 year ago.
Category: Small Engine
Expert:  Hank F. replied 1 year ago.

Hello, my name is ***** ***** I am going to assist you with this.

What is the model number of the genset?

Customer: replied 1 year ago.
8HDKAK-1046N spec N
Sorry didn't back to you sooner, was out of town,
Expert:  Hank F. replied 1 year ago.

In your serial number, there is a letter before the 1306.....

What is that letter?

Customer: replied 1 year ago.
Sorry, the letter is L
Expert:  Hank F. replied 1 year ago.

OK, thanks.

This unit is still under warranty, so we are going to be limited in what we can do without voiding that warranty.

I will take you as far as I can, but it may come to a point that you will need to take it to an authorized Onan repair facility to have it repaired under warranty.

The first thing I need you to do is to check and see what fault code is set in the controller.

Go to the genset and use the switch on the set itself.
Press 'Stop' 3 times within 5 seconds. The light in the switch will start flashing.
If the light flashes 3 times, pauses for 3seconds, and flashes 3 more times, press and immediately release 'Stop' one more time.

This will put the controller into Fault Read Mode.

The light will flash (X) number of times, pause for 1 second, and flash for(X) number of times again. Count the flashes before and after the pause.

This will be the Fault Code.

Example: 2 rapid flashes, 1second pause, 5 rapid flashes is a Fault Code 25.

There may be more than one Fault Code stored, so watch the light very carefully. If there is more than one code, it will display them all in order, and then start over again.

Be very careful not to misread a first level fault code (single digit code) as a second level fault code (double digit code).

The way to tell the difference is by the length of the pauses.

There is a 1 second pause between digits of a second level code, and a 3 second pause between codes.

For example, if it is flashing 2 times, 1 second pause, flashing 2 times, 3 second pause and repeating, then this is a second level fault code of 22.

If it is flashing 2 times, 3 second pause, flashing 2 times, 3second pause and repeating, then this is a first level fault code of 2.

What Fault Code are you getting?


Next, remove the maintenance access panel on the front of the genset.

Inspect all accessible fuel lines for evidence of leakage/seepage. If any are noted at all, it must be taken care of first.

Assuming there is no leakage or seepage, do a fuel flow test.

To do a fuel flow test, get underneath the genset, and remove the return fuel line. It is marked on the side of the genset.

Attach a piece of fuel hose to the nipple, and run the hose into an empty container of at least 1 quart capacity.

Press and hold the STOP/PRIME button for exactly 1 minute.

In 1 minute, it should pump a minimum of ½ pint of fuel. If it does not, there is an issue with the pump or the supply lines.


Let me know what you find.

Expert:  Hank F. replied 1 year ago.

Did you get the fault code and do the fuel flow test?